With market pressure driving ever expanding service offerings, telecommunication operators are offering a service combination known as Triple-Play services. Triple-Play services combine high-speed internet access, television programming and voice over internet protocol (VOIP) communications. In an effort to reliably provide these services, telecommunication operators have implemented multiprotocol label switching (MPLS) multicast trees to deliver the services to the end users. FIG. 1 illustrates a prior art MPLS network 102 connected to an internet protocol (IP) core network 104, providing the media source, and a digital line subscriber access multiplexer (DSLAM) 106. The MPLS network includes root nodes 108 (connected to routers 114 on the IP network), leaf nodes 110 (connected to a DSLAM), and routers 112 connecting the MPLS root nodes 108 to the MPLS leaf nodes 110.
Typically, telecommunication providers employ over-provisioning techniques for redundancy by delivering the same content, from multiple root nodes, over several multicast trees to a set of routers/switches, the leaf nodes, positioned at the edge of the MPLS network. Under normal operating conditions, the router/switch leaf nodes receive the communications from a primary tree with another tree acting as a secondary or backup communication path. If the primary tree fails, then the secondary tree can step in and deliver the content from a root node to the leaf nodes.
Detecting a primary tree failure is typically accomplished with a Bidirectional Forward Detection (BFD) mechanism to reduce the time required for detection. In a typical prior art embodiment, a BFD transmitter is installed on the root node of each multicast tree and the BFD packets are replicated to each of the leaf nodes of the multicast tree. In this embodiment, each leaf node detects the failure of a path, or the source, by monitoring the arrival of the incoming BFD connectivity detection packets.
The existing BFD solutions to detecting a tree failure have two drawbacks related to failures upstream of the root node. In the case of the first failure, a failure between the MPLS network and Internet Protocol (IP) network, a leaf node cannot detect the failure because the BFD mechanism is still operational. Consequently, the failure must be detected by MPLS signaling mechanism such as Targeted Label Distribution Protocol (T-LDP) or static Pseudowires (PW) status signaling. Implementing these additional MPLS signaling mechanisms increases both the development and the maintenance costs for a system capable of delivering real-time content with acceptable levels of recovery.
In the case of the second and more damaging failure, a failure in the IP core network, the detection of the communications failure and the subsequent recovery from the failure will rely on IP resiliency. The issue associated with this type of recovery mechanism is the time required for the IP resiliency mechanism to detect the failure and respond. This longstanding mechanism cannot meet the fast service recovery time of less than fifty milliseconds as required by the services provided in a “Triple-Play” package.
Accordingly, market pressure is building for a method and system capable of providing a deterministic communication failure detection and recovery in an MPLS system of less than fifty milliseconds. It is desirable that the method and system not require any signaling facilities associated with the MPLS network.